Effect of Initial Grain Size on High‐Temperature Tensile Deformation and Microstructural Evolution of GH2907 Alloy

To investigate the effect of grain size on the tensile deformation behavior and dynamic softening mechanisms of GH2907 alloy at 500 and 600 °C, fine‐grained (FG) and coarse‐grained (CG) specimens were prepared via solution treatment. High‐temperature tensile tests were performed at 500 and 600 °C, combined with mechanical testing, fractographic observation, and EBSD characterization. Results show that dynamic recovery dominates the softening process in both FG and CG specimens at 500 °C. The FG specimen exhibits a higher KAM‐based local misorientation response and better deformation compatibility associated with its higher grain‐boundary density. At 600 °C, the FG specimen exhibits enhanced recovery and progressive subgrain evolution, together with an EBSD‐classified recrystallized fraction of 14.8% and reduced local lattice distortion, while retaining typical microvoid‐coalescence ductile fracture characteristics. In contrast, the CG specimen shows no obvious recrystallization at 600 °C, and its microstructural evolution is dominated by dynamic recovery, leading to severe stress concentration and intergranular fracture. Grain size significantly affects the strength–ductility balance and fracture behavior of GH2907 alloy by influencing grain‐boundary density, local misorientation evolution, and dynamic softening responses.